Painting depends on your state of mind and everything affects your state of mind. Use music, food, your workspace, your relationships and your intention to your advantage. Create an ecosystem of creativity for yourself.

[...] what concerns us here is not imagination itself, but rather creative imagination; the faculty that helps us pass from the level of conception to the level of realization.- Igor Stravinsky, The Poetics of Music

Its kind of hard to critique your work since its somewhat stylized
but on average the proportions of the face are a little off.
The face is too small for the skull and the forehead is too long.
With the values you are a little extreme and go too dark too quickly.
Try to be more consistent with contrast and remember that the background has less contrast
than the foreground

I wanted to say that I really enjoy your style, your pixel art in particular. Great colours and shading, I really love pixel art but never got anywhere near your level haha. Very refined stuff. Pretty cool subject matter too, it all seems connected. You know what you like.

"[...]as we gain facility of hand and travel further afield, we discover that we have a key to unlock the wonders of art and nature, a method of conjuring up forms at will: a sensitive language capable of recording and revealing impressions and beauties of form and structure hidden from the careless eye[...]"
-Walter Crane, 'Line & Form'